Is it appropriate to sell just a Steam Key with no download?

Is it appropriate use of this site to only sell a product that is only a Steam Key? By this I mean, there would be no download for the game provided. I ask this because my game does not run outside the Steam environment.

We prefer people to sell files with their game, but we do allow some people to sell only Steam keys since for some game's it's not possible to make a standalone build. If you'd like to do that please send a message to support@itch.io and we can enable it on the project page you need it for. You should have the page for the game already created, but it doesn't need to be published.